With the recoverable reserves of light oil decreasing and oil production technology advancing constantly, the percentage of heavy oil in crude oil production will keep increasing in the 21st century. Heavy oil is a complex mixture rich in asphaltene and resin. Its main features include high viscosity, small difference in oil/water density and low mobility. Since asphaltene and resin in the heavy oil are natural surfactants, the heavy oil and formation water would form the emulsion in the process of heavy oil production more or less. Besides, the high viscosity of heavy oil mainly due to the high content of asphaltene and resin. Therefore, demulsification and dehydration of heavy oil are indispensable steps in oilfield production.
With the continuous development of petroleum industry, the demand for demulsifier is increasing and the performance requirement for it will be much higher. Thus, it is necessary to conduct research to develop new improved demulsifiers. Petroleum demulsifier has over 90 years of history, and the first patent that mentioned it was published by W. S. Barnickel in 1949. The inventor suggested to demulsify the water oil emulsion at 35˜60° C. by using a 0.1% FeSO4 solution. From the 1920s, surfactants started to be used as demulsifiers, and the main types included fatty acid salt, arenyl or alkyl hydrocarbon sulfonate, castor oil, sulfonate, naphthenate and so on. In 1940s to 1970s, nonionic surfactant has been used as demulsifier gradually, and alkylphenols including nonyl phenol, isooctyl phenol, octyl phenol, and isobutyl phenol were used. Though these nonionic surfactants have good abilities in resistance to salinity, the demulsification effects are not so good. Then in the late 80s, an ever increasing amount of efforts were put into the research and development of new types of demulsifiers. As a result, a third generation of demulsifiers based on high molecular weight polyether was developed, with much improved performance.
Currently, heavy oil demulsification still face many difficulties. Much of time, the demulsifier could be effective only when heated over 90° C. This invention aims to solve the problems of high temperature and high cost of energy in heavy oil demulsification. Highly efficient, low temperature heavy oil demulsifiers have been screened, discovered, and described herein.